DIFFUSION IN POLYMERS WITH VARYING ACCESSIBILITY

This paper considers the problem of describing quantitatively the proc ess of diffusion in polymers attended with plasticization of their amo rphous phase. A consequence of such plasticization is that the volume accessible for the penetrant molecules continuously increases during t he course of their sorption. Assuming that the rate of the relaxation processes is far greater than that of diffusion, an equation has been generated to describe sorption in a matrix with varying accessibility. The numerical solution of this equation using the experimental data f or a polyamide-water system demonstrates that sorption in the matrix w ith increasing accessibility is slower than sorption in a hypothetical matrix with constant accessibility equal to the portion of the amorph ous phase. At the same time, the concentration of the penetrant in the former case proves higher in any point of the polymer specimen. The r esults obtained are important for calculating the rate constants for c hemical reactions that in a polymer matrix are proceeding in the diffu sion-kinetic mode.